This invention relates to a pulse repetition frequency tracker and particularly with an improved means of acquiring and locking to a single pulse train within a two octave frequency range and maintaining lock through periods of missing input information.
In many communications systems it is desirable if not an essential function that a pulse repetition frequency tracker be included. This type of tracking provides the mechanism by which the arrival of a pulse can be predicted and/or anticipated. A typical use of this information would be to correlate it with the incoming received input and thus lessen the chance of false alarms.
The prior art systems utilizing conventional techniques for pulse repetition tracking have several limitations. In many applications the pulse repetition tracking is confined to a small frequency spectrum. Attempts to extend the range beyond one octave of harmonic locking may leave pulses undetected. The possibility of a wider frequency range may be obtained through the use of a standard phase lock loop. However, this device locks to a varying phase angle to the input as a function of the operating frequency.
A further limitation of the prior art systems which is common in the conventional trackers and typical of phase lock loops is the difficulty in handling multiple signal inputs. In actual practice, many input signals are present and it is essential to acquire and lock to a particular single input signal.